has two meanings: As an adjective it means unknown, strange, unusual; but as an adverb it means very - as unco good, unco glad, etc. The “unco guid” are the pinchbeck saints, too good by half.
“The race of the `unco guid' is not yet quite extinct in Scotland.” —A Daily Journal.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894
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